Boil the milk with salt. Add millet flakes and swell for 1/2 hour.
Mix light butter, sugar and egg yolks until creamy. Add the cooled porridge, hazelnuts and lemon zest, stir everything together until well combined. As a last step, stir in the stiffly beaten snow. Cut the plums into cubes and mix into the dough.
Pour the batter into a greased baking dish, spread butter flakes evenly on top and bake in a heated oven at 180 °C for 60 minutes.
Vanilla yogurt sauce: Stir all ingredients together.
Tip: Use creamy natural yogurt for an even finer result!